This invention relates to mobile crop harvesters for harvesting hay and forage or grain, such as a mower conditioner or windrower, of the type having a laterally elongated crop harvesting header and, more particularly, to a novel means of suspending the header from the frame of the harvester.
In machines of this type the header is usually mounted on a mobile frame in a manner providing a lowered operating position with the ground shoes engaging the ground and a raised transport position well above the operating position to provide a considerable amount of ground clearance for transport. The header is usually mechanically or hydraulically counterpoised such that the weight thereof is partially balanced so that the force reaction at the ground shoes is less than the weight of the header which allows the header to follow the ground irregularities encountered in normal operation with less draft loading and consequently less stressing of frame components than would otherwise be experienced. Floation of the header is usually required only in the lower portion of the lift range and is quite acceptable and effective at relatively slow operating speeds. However, in modern equipment, operating speeds have increased and inertial loads must be considered. Since these are mass related rather tha weight related, counterpoising alone is ineffective. Accelerations especially of the center of mass, must be reduced. Thus, a header suspension system which provides for less displacement of the center of mass of the header than of the cutterbar during the float range would be desirable. A simple means of providing this desirable float action is with a fixed pivot between the header and the carrying frame, such as illustrated in Bornbin et al. U.S. Pat. No. 3,625,537, since the center mass is usually rearward of a cutterbar and the fixed pivot rearward of both. However, with this system any part rearward of the pivot moves progressively closer to the ground as the header is raised; there is no lateral floatation of the header and the pivot must be located substantially higher than the position of the cutterbar in order to provide adequate ground clearance creating an undesirable moment opposing the floatation means caused by crop resistance and the friction of the gage shoes on the ground.
Although conventional four bar suspension linkages such as illustrated in Case et al. U.S. Pat. No. 3,835,628 or Schoeneberger U.S. Pat. No. 3,958,399, may be designed to overcome one or more of these problems, it is believed that only a crossed four bar linkage described hereinafter produces all the desirable results. It will be appreciated that the term "four bar linkage" as applied to a machine of this type does not mean that all the links are in the same plane but rather refers to a side projection of the three dimensional header and frame assembly.